Compositions for sizing siliceous fibers and process



United States Patent 3,192,089 COMPOSITEQNS FOR SIZING SILICEOUS FIBERS AND PROCESS Harold A. Clark, Midland, Mich, assignor to Dow Corning Corporation, Midland, Mich, a corporation of Michigan No Drawing. File-d Mar. 19, 1962, Ser. No. 180,839 6Claims. (Cl. 156-466) This invention relates to an organosilicon-containing homogeneous solution for use in sizing siliceous fibers to form strands and to the process for sizing these fibers.

The technique for sizing glass fibers is described in Biefeld, US. Patent 2,392,805. As described in this patent, a plurality of molten glass streams issuing simultaneously from many orifices in the underside of a bushing of a glass melting furnace are attenuated simultaneously intofine fibers by a winding drum'about which a strand of gathered fibers are wound. Several hundred fibers can be simultaneously drawn inrthis manner and combined to form a strand. Just before the fibers are gathered into a strand, a size can be applied by either a roll applicator or wiper pad.

3"Afi61 a package of these strands has been built-up upon the winding drum, the package is then removed. A rovingcan be made from these packages by pulling the strand from the inside of the package and combining severalstr'ands together in a twisting operation. The strands can-also be-pulled from the package to form threads which are used to prepare a glass cloth. Substantially this-same technique is used for. other types of siliceous fibers, such as quartz fibers.

' It is necessary to apply a size to these fibers to prevent fuzzing of the strand due to breakage of the'fibers during the gathering operation. It is also necessary to retain this size in order to prevent fuzzing of thestrand during the roving or weaving operation and to insure that the fibers are bound together in the strand. Various compositions have been applied as the size for siliceous fibers. Starch and gelatin compositions in aqueous medium havebeen used. However, after starch-sized fibers have been made into a rov ng or cloth, it is essential to remove the starch size in order to use the roving or cloth with various resins to'makemolded and laminatedarticles. Although the starch size can be removed by heat cleaning, this is anexpensive and time-consuming operation. Furthermore; the tensile strength of the fiber is substantially reduced by this operation. moved from quartz fibers, the fiber often breaks, thus rendering the roving or clothunsatisfactory. Consequently, it is desirable to provide -a'size which need'notbe removed from roving or cloth in order to incorporate the material into structural materials in combination with Although other sizes such as polyvinyl acetate resins. and low molecular" weight polyester resins, have been used, these have not proven to be very satisfactory when laminated products are made with these fibers and the bonding resins are heat-aged. Some sizes do not lubricate the fibers enough to prevent breakage during the twisting operation. the individual fibers together into a strand. Another disadvantage of many of the conventional sizing compo- 1 sitions is that their heat stability and other physical properties are poorer than the resin with which the fibers are to be incorporated. This is especially true when these rovings or cloth are used with a silicone resin. There- When a starch size is re-.

Many sizes do not satisfactorily bind Her:

position which will increase the abrasion resistance ofsiliceous fibers and which will bond the fibers together into a strand. It is a further object to produce a satistory size for quartz fibers. Another object is to produce asize which has heat stability properties comparable to silicone resins and which can be incorporated with a silicone resin to produce structural materials.

- These objects are obtained by a homogeneous solution for sizing siliceous fibers to form strands, said solution produced by mixing (1) Methoxysilanes of the general formula wherein n has an average value of from 0.2 to 1.0, m has an average value of from 0.65 to 1.05 and the average value of m+n is from 1.25 to 1.65, said methoxysilanes containing (A) No more than 75 mol percent phenyltrimethoxysilane, (B) No more than 15 mol percent dimethyldimethoxysilanc, (C) No more than 35 mol percent monomethyltrimethoxysilane, and p (D) From 25 to 65 mol percent methoxysilanes of the general formula (C H )RSi(OCI-I wherein R is selected from the group'consisting of phenyl and methyl radicals, there being no more than 10 mol percent diphenyldimethoxysilane with (2) Suificient water to obtain an organosilicon solids concentration of from 2 to 10 percent by weight based upon the total weight of the solution. This homogeneous solution is prepared by mixing the methoxysilanes with water. It is necessary in this initial mixing that there be at least one mol of water per mol of methoxy radicals in the silanes. Preferably, .the amount of water is from 2 to 3 mols of water per mol of methoxy radical. The mixture is then agitated until a homogeneous solution is obtained. This homogeneous solution is then diluted with sufiicient water to obtain the organosilicon solids concentration of from 2 to 10 percent by weight based upon the total weight of the solution. The preferred organosilicon solids concentration is from 3 to 7 percent by weight. If desired, the mixture can be diluted to the desired organosilicon solids concentration with a water-methanol mixture. It is also often desirable to add methanol to the solution when diphenyldimethoxysilane is incorporated in the silane mixture. Alternatively, the methoxysilanes can initially be mixed with sufficient water to vyield the desired organosilicon solids concentration. The silanes can bepremixed and then added to the water or'the silanes can be individually added to the water.

In order to facilitate the production of :a homogeneous solution, it is desirable to employ a mild hydrolysis of ion free water is not essential to the practice of this invention. 7

The methoxysilanes can be represented by the formula (CH (C H Si(OCH wherein n has an average value of from 0.2 to 1.0 and m has an average value of from 0.2 to 1.0 and in has an average value of from 0.65 to 1.05. There is an average of from 1.25

to 1165 total methyl and phenyl radicals per silicon atom in the methoxysilanes. In order to obtain an average of 1.9 from 0.6 5 to 1.05 phenyl radicals per silicon atom, it is essential that the methoxysilanes contain from 25 to 65 mol percent phenylmethyldimethoxysilane or from 25 to 65 -mol percent of a combination of phenylmethyldimethoxy-silane and diphenyldimethoxysilane. Not more than mol percent (based upon the total methoxysilanes) of diphenyldirnethoxysilane should be used. Thus, a combination of from to 55 mol percent phenylmethyldirnethoxysilane and 10 mol percent diphenyldimethoxysilane can be used.

Since the methoxysilanes also contain from 0.2 to 1 silicon-bonded methyl radicals per silicon atom, it is necessary to use some methyl-containing methoxysilanes. These methyl radicals are present in the phenylmethyldimethoxysilane as previously defined. In addition, the methoxysilane combination can contain no more than 15 mol percent dimethyldimethoxysilane and no more than 35 mol percent monomethyltrimethoxysilane and no more than 75 mol percent phenyltrimethtoxysilane. It should be pointed out that there must be an average of from 1.25 to 1.65 total methyl and phenyl radicals per silicon atom and an average of from 0.65 to 1.05 total phenyl radicals per silicon atom. However, in all cases the above average degrees of substitution must be followed.

The preferred methoxysilane,combination contains from to 40 mol percent phenyltrimethoxysilane, from 15 to 35 mol percent methyitrimethoxysilane and from 30 o 50 mol percent phenylmethyldimethoxysilane and sufiicient water to yield an organosilicon solids concentration of from 3 to 7 percent by weight based upon the total weight of the, solution,

Although not essential to this invention, other ingredients such as lubricating agents and antistatic agents can be incorporated into the homogeneous solution. This homogeneous solution can be applied to the siliceous fibers by an presently conventional means such as roll applicator or by wiping the composition onto the fibers as they are formed. After the size has been applied to the fibers, the fibers are gathered into a strand formation and wound upon a drum. The wound package of strands is then removed from the drum and heated at a temperature sufficient to remove the water and partially condense the organosilicon material so that the fibers are bound tog ther in the strand. The exact temperature and time of this heating step depends upon the organosilicon mixture used and numerous other factors. Temperatures of from 38 to 80 C. are preferred. The best results are obtained when the package is vacuum dried for several hours within this temperature range. This heating step is essential in order to remove the water and methanol from the size r composition and to insure that the individual fibers are bound together in the strand. This package can then be unwound and several strands twisted into a roving or a thread to be placed into a cloth. This roving or cloth can then be used as an element in structural materials in combination with resins. The glass roving or cloth treated variety of applications, such as in the manufacture of structural members, for electrical insulation and thermal.

insulation. The roving or cloth is especially useful as an element in combination with a resin for molding compositions. Examples of resins which can be used in conjunction with these fibers include silicone, epoxy, phenolformaldehyde and acrylic resins. The silicone resins are preferred. Examples of suitable siliceous fiber-s include glass and .quartz fibers.

The sizing composition of this invention reduces breakage and static problems as the fibers are gathered into strands and as the strands are pulled from the wound package and twisted into roving or weaved into a cloth. Another advantage of this size composition is that it need not be removed in order for the fibers to be incorporated withresins. This sizing composition also has heat stability properties comparable to silicone resins .and augments the properties obtained when the fibers are 7 following silane mixtures.

4 incorporated with such resins. This sizing composition is especially useful for quartz fibers which are otherwise subject to excessive breaking during the heat cleaning operation which is necessary if a less heat stable size. is employed. The use of this sizing composition eliminates the need for the heat cleaning step which is expensive and results in the reduction of the tensile strength of the glass fibers and in excessive breakage with quartz fibers.

The following examples are illustrative only and should not be construed as limiting the invention which is properly delineated in the-appended claims.

Example 1 Various sizing solutions were prepared by using the The silanes were added to a sufficient quantity of deionized water containing .1 per cent by weight acetic acid to yield about 6,000 grams of solution. After the silane mixture was added to the water, the solution was agitated with a mechanical mixeruntil a single phase formed.

A. 466 grams of a mixture containing 40 mol percent (1.07 mols) phenyltrimethoxysilane, 3 0 mol percent (.8 mol) phenylmethyldimethoxysilane and 30 mol percent (.8'mol) methyltrimethoxysilane.

B. 444 grams of a mixture containing 75 mol percent (1.72 mols) phenyltrimethoxysilane and 25 mol percent (.57 mol) phenylmethyldimethoxysilane.

C. 365.5 grams of a mixture containing 28 mol percent (123.5 g.) of phenyltrimethoxysilane, 29 mol percent (82 g.) methyltrimethoxysilane and 43 mol percent (160 g.) phenylmethyldimethoxysiiane. 12 grams of a commercial amine fiber lubricant wasadded to this mixture.

Each of the above solutions. was used to size glass fibers. The size was applied after. the fibers had been drawn from the 'bushing but before they had been gathered. These fibers were then gathered'into a strand and wound upon a winding drum. The package of wound fibers was then removed and baked for 16 hours at 113 C. Strands were pulled from the inside of five such wound packages and made into a five-end roving. The silicone size lubricated the fibers sufiiciently well that there was no breaking during forming. The glass fibers which were sized wih mixture (A) picked up between 0.4 to 1.6 percent by weight of silicone solids. This was measured by ignition loss after the package had been baked.

Example 2 The following silane mixtures were mixed wth sufficient water containing .1 percent by weight acetic acid to yield approximately 6,000 g. of sizing solution. The

silane mixtures were merely added with the water and agitated until a single phase formed.

A. 520 grams of a mixture containing 35 mol percent (1 mol) of phenyltrimethoxysilane, 15 mol percent (.43 mol) of methyltrimethoxysilane and mol percent (1.45 mols) of phenylmethyldimethoxysilane. 10.8 grams of a commercial amine fiber lubricant was added to this mixture.

B. 571 grams of a mixture containing 15 mol percent (.5 mol) of phenyltrimethoxysilane, 35 mol percent (1.2 mols) of methyltrirnethoxysilane and 50 mol percent (1.7 mols) of phenylmethyldimethoxysilane.

C. 538 grams of a mixture containing 25 mol percent (.77 mol) of phenyltrimethoxysilane, 25 mol percent (.77 mol) of methyltrimethoxysilane and 50' mol percent and wound upon a drum. The wound package was then removed and vacuum dried under a partial vacuum for several hours at about 60 C. Strands were then pulled from the inside of the wound package and combined into a three-end roving. The roving was then impregnated with a commercial silicone laminating resin and fabricated into a filament wound construction which possessed excellent electrical properties. There were no interruptions in the fiber forming operation and no fuzzing or static problems in the roving operation.

Example 3 A sizing solution was prepared by adding 431 grams of a mixture containing 60 mol percent (1.31 mols) phenyltrimethoxysilane, 30 mol percent (.66 mol) phenylmethyldimethoxysilane and mol percent (.22 mol) diphenyldimethoxysilane to 5,569 grams of deionized water containing .1 percent by weight acetic acid. The solution was agitated with a mechanical mixer until a single phase formed. This sizing solution was applied after the fibers had been drawn from the bushing but before they had 7 been gathered. These fibers were then gathered into a strand and wound upon a winding drum. The package of wound fibers was then removed and baked for 16 hours at 113 C. Strands were pulled from the inside of five such wound packages and made into a five-end roving. The silicone size lubricated the fibers so that there was no breaking at the bushing.

The roving was drawn through a silicone molding resin slurry in such a manner that the resultant molding compound was 50 percent glass by weight and 50 percent resin and slurry solids by weight. The roving was then heated in an air circulating oven at 150 C. for 75 seconds to remove the solvent. The roving was then cut into inch lengths. This chopped roving compound was then compression molded into bars A" x /z x 6". Each bar was molded from a charge of 21 g. of compound. Three bars were molded simultaneously at a pressure of 16 tons and at a temperature of 175 C. The bars were removed from the mold after cooling and after-baked for 2 hours at 260 C. The average fiexural strength of the three bars tested was 11,800 p.s.i.

That which is claimed is:

1. A homogeneous solution for sizing siliceous fibers to form strands suitable for application to the fibers before they are gathered into a strand, said solution being produced by mixing (1) methoxysilanes of the general formula where n has an average valueof from 0.2 to 1.0, m has an average value of from 0.65 to 1.05.and the average value of m-i-n is from 1.25 to 1.65, said methoxysilanes containing (A) no more than 75 mol percent phenyltrimethoxysilane, (B) no more than mol percent dimethyldimethoxysilane, (C) no more than 35 mol percent methyltrimethoxysilane, and (D) from 25 to 65 mol percent methoxysilanes of the general formula (C H )RSi(OCH wherein R is selected from the group consisting of phenyl and methyl radicals, there being no more than 10 mol percent diphenydimethoxysilane with (2) sufiicient water to obtain an organosilicon solids concentration of from 2 to 10 percent by weight based upon the total weight of the solution. 7 2. A method for sizing siliceous fibers to form strands, which comprises (1) coating the siliceous fibers before being arranged into strand formation with the homogeneous solution of claim 1, arranging the fibers into strand form, and

(2) then heating the fibers when in strand form at a temperature sufficient to remove the water and partially condense the organosilicon material so that the fibers are bound together in the strand.

3. A homogeneous solution for sizing glass fibers to form strands suitable for application to the fibers before they are gathered into a strand, said solution being produced by mixing (1) methoxysilanes, said methoxysilanes consisting essentially of from (A) 20 to 40 mol percent phenyltrimethoxysilane, (B) from 15 to 35 mol percent methyltrimethoxysilane, and (C) from 30 to 50 mol percent phenylmethyldimethoxysilane with (2) sufficient water to obtain an organosilicon solids concentration of from 3 to 7 percent by weight based upon the total weight of the solution.

4. A method for sizing glass fibers to form strands, which comprises (1) coating the glass fiber before being arranged into strand formation with a homogeneous solution of claim 3, arranging the fibers into strand form, and

(2) then heating the fibers when in strand form at a temperature sufiicient to remove the water and partially condense the organosilicon material so that the fibers are bound together in the strand.

5. A homogeneous solution for sizing quartz fibers suitable for application to the fibers before they are gathered into a strand, said solution being produced by mixing (1) methoxysilanes, said methoxysilanes consisting essentially of from I (A) 20 to 40 mol percent monophenyltrimethoxysilane, (B) from 15 to 35 mol percent monomethyltrimethoxysilane, and (C) from 30 to 50 mol percent phenylrnethyldi methoxysilane with (2) sufficient water to obtain an organosilicon solids concentration of from 3 to 7 percent by weight based upon the total weight of the solution.

6. A method for sizing quartz fibers to form strands which comprises (1) coating the quartz fiber before being arranged into strand formation with a homogeneous solution of claim 5, arranging the fibers into strand form, and

(2) then heating the fibers when in strand form at a temperature suificient to remove the water and partially condense the organosilicon material so that the fibers are bound together in the strand.

References Cited by the Examiner UNITED STATES PATENTS 2,392,805 1/ 46 Biefeld 260-292 2,643 ,964 6/5 3 Smith-Johannsen.

2,718,483 9/55 Clark 117126 2,723,215 11/55 Biefeld.

2,763 ,629 9/ 5 6 Gottfurcht.

2,799,598 7/57 Biefeld et al. 156167 X 2,832,754 4/58 Jex et al.

2,891,885 6/59 Brooks.

2,906,734 9/59 Clark 26046.5 3,079,281 2/63 Dexter et al. 117126 FOREIGN PATENTS 596,83 3 1 48 Great Britain. 767,726 2/57 Great Britain.

OTHER REFERENCES Vanderbilt, B. M.: Effectiveness of Coupling Agents in Glass-Reinforced Plastics, Modern Plastics, September 1959, pages 125-127, 130, 132, 198, 200.

EARL M. BERGERT, Primary Examiner. 

1. A HOMOGENEOUS SOLUTION FOR SIZING SILICEOUS FIBERS TO FORM STRANDS SUITABLE FOR APPLICATION TO THE FIBERS BEFORE THEY ARE GATHERED INTO A STRAND, SAID SOLUTION BEING PRODUCED BY MIXING (1) METHOXYSILANES OF THE GENERAL FORMULA 